Tumors of Penis and Prepuce in Male Animals

Tumors of the penis and prepuce in male animals are abnormal growths that can develop on the penile tissues or the preputial sheath. These tumors may be benign or malignant and can affect animals such as bulls, dogs, stallions, and other male livestock.

Tumors of the penis and prepuce cause phimosis or paraphimosis and prevent normal intromission.

Bulls

The only significant tumor in bulls is the transmissible fibropapilloma caused by a virus. These tumors appear as single or multiple firm, cauliflower-like growths.

Young bulls (9–18 months of age) are commonly affected. When grouped together, young bulls frequently mount each other, which may cause preputial injuries that provide an entry point for lesions.

Injury to the penis occurs when young bulls breed before the complete separation of the penis and prepuce.

Haemorrhage from the sheath after service and refusal to copulate are frequently observed in bulls with penile tumors.

Treatment

Spontaneous recovery from infectious fibropapillomas usually occurs within 4 months.

If the tumors are multiple on the penis, treatment becomes difficult. Wart vaccine can be tried, but its effectiveness in affected bulls is questionable.

Semen from affected bulls should not be used due to the risk of transmitting the virus to cows.

Surgical removal under pudendal nerve block can be performed.

Stallion

Tumors are very uncommon in horses. When present, they are usually squamous cell carcinomas of low malignancy. These should be differentiated from granulomas caused by Habronema larvae.

Treatment

The occasional squamous cell carcinoma can be removed by a liberal incision or if necessary by amputation of the penis.

Dogs

The transmissible venereal tumor (TVT) is the most common tumor of the penis and prepuce. It spreads by coitus.

Licking of the vulva or preputial discharge rarely transmits the disease. Intact cells must be transplanted to transmit the tumor.

The incubation period for TVT is 5–6 weeks, and all breeds of dogs are susceptible. It is characterized by a discharge of bloody, fetid exudate from the prepuce of the male.

When the penis is exposed, grayish-red nodular growths are observed on the penis and prepuce. The tumor masses are friable and bleed when handled.

In advanced cases, the tumor may also involve the inguinal lymph gland. The tumor ulcerates easily.

The transmissible venereal tumor has been reported worldwide but is most common in tropical countries.

Papillomas, squamous cell carcinomas, sarcomas, and other tumors may also occur on the sheath or penis of dogs.

Treatment

In dogs, surgery may be indicated. The earlier the surgery is performed, the better the chances of a successful outcome.

In severe cases where it is difficult or impossible to remove all the involved tissue, radiation therapy may be recommended.

Medical treatment with vincristine is given at a dose rate of 0.025 mg per kg body weight, administered slowly intravenously diluted in saline or distilled water, and repeated at 7 day intervals until complete regression.